4-9
©
2012 Mobile Climate Control
T-348 Rev. 07/2012
4.8.2 Adding Full Charge
a. Install manifold gauge set at the compressor suc
tion and discharge service valve ports. See figure
Figure 4-6.
b. Evacuate and dehydrate system. Refer to para
graph 4.7.
NOTE
Evacuation can be performed at the com
pressor but liquid charging should only be
done at the charge isolation valve on the bus
roof (See Figure 4-6, Item 11) or the dis
charge line service port (See Figure 4-6, Item
2).
c. Place appropriate refrigerant cylinder on scales.
Prepare to charge liquid refrigerant into the system
by connecting the charging hose from refrigerant
cylinder (20) to the charge isloation valve(11).
d. Energize the Liquid Line Solenoid Valve (LLSV)
(13) using an external power source (24 VDC).
e. Note weight of refrigerant and cylinder.
f. Open cylinder valve (20) and purge hose at charge
isolation valve (11).
g. Midseat filter drier inlet valve to allow liquid refrig
erant to flow into the low side.
h. When correct charge has been added, refer to
paragraph 1.5, close cylinder valve.
i. Remove 24 VDC from Liquid Line Solenoid .
j. Backseat charge isolation valve.
k. Check charge level in accordance with the proce
dures of paragraph 4.8.1.
4.8.3 Adding Partial Charge
a. Install manifold gauge set at the compressor suc
tion service valve. See Figure 4-6.
b. Place appropriate refrigerant cylinder on scale.
Prepare to charge vapor refrigerant by connecting
charging hose from container to center connec
tion on gauge manifold. Purge air from hoses.
c. Run the unit in the cool mode as described in sec
tion 4.8.1. With the suction service valve mid
seated, open the refrigerant cylinder valve and add
vapor charge until the white balls are floating and a
liquid level is detected in the receiver sight glasses.
d. Backseat the suction service valve. Close the vapor
valve on the refrigerant drum and note weight. Re
move the manifold gauge set and replace all valve
caps.
4.9 CHECKING FOR NONCONDENSIBLES
To check for noncondensibles, proceed as follows:
a. Stabilize system to equalize pressure between the
suction and discharge side of the system.
b. Check temperature at the condenser and receiver.
c. Check pressure at the filter-drier inlet service
valve.
d. Check saturation pressure as it corresponds to the
condenser/receiver temperature using the Tem
perature-Pressure Chart, Table 4-4.
e. If gauge reading is 3 psig
(0.20 bar)
or more than the
saturation pressure in step d, noncondensibles are
present.
f. Remove refrigerant using a refrigerant recovery
system.
g. Evacuate and dehydrate the system. Refer to para
graph 4.7.4.
h. Charge the unit. Refer to paragraph 4.8.2.
4.10 CHECKING AND REPLACING HIGH OR LOW PRES-
SURE SWITCH
WARNING
Do not use a nitrogen cylinder without a
pressure regulator
WARNING
Do not use oxygen in or near a refrigera
tion system as an explosion may occur.
a. Disconnect wiring and remove switch from unit.
All units are equipped with a schrader valve at the
pressure switch connections.
b. Connect switch to a cylinder of dry nitrogen. See
Figure 4-7.
